This disclosure relates to controlling clearances within a gas turbine engine and, more particularly, to control of clearances between blade tips and blade outer air seals.
A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section. The compressor section typically includes low and high pressure compressors, and the turbine section includes low and high pressure turbines.
A speed reduction device such as an epicyclical gear assembly may be utilized to drive the fan section such that the fan section may rotate at a speed different and typically slower than the turbine section so as to provide a reduced part count approach for increasing the overall propulsive efficiency of the engine. In such engine architectures, a shaft driven by one of the turbine sections provides an input to the epicyclical gear assembly that drives the fan section at a reduced speed such that both the turbine section and the fan section can rotate at closer to optimal speeds.
The compressor sections and turbine sections of the gas turbine engine include arrays of rotatable blades. Tips of the blades seal against blade outer air seals during operation. One factor influencing the efficiency of the operating engine are the clearances between tips of the blades and the relatively stationary blade outer air seals.
Referring to prior art FIG. 1, many gas turbine engines include clearance control rings 4 to control the position of the blade outer air seals 6 relative to the rotating arrays of blades 8. Current bolted flange arrangements 4 are difficult to machine and assemble. Current bolted flanges 4 restrict capability to adjust to achieve specific blade tip clearances.